1. Field of the Invention
The present invention relates to contact lenses having improved tear exchange, and more particularly to contact lenses having fractal features formed in the periphery of the back curve side thereof to improve tear exchange.
2. Discussion of the Related Art
Contact lenses or contacts are simply lenses placed on the eye. Contact lenses are considered medical devices and may be worn to correct vision and/or for cosmetic or other therapeutic reasons. Contact lenses have been utilized commercially to improve vision since the 1950s. Early contact lenses were made or fabricated from hard materials, were relatively expensive and fragile. In addition, these early contact lenses were fabricated from materials that did not allow sufficient oxygen transmission through the contact lens to the conjunctiva and cornea which potentially could cause a number of adverse clinical effects. Although these contact lenses are still utilized, they are not suitable for all patients due to their poor initial comfort. Later developments in the field gave rise to soft contact lenses, based upon hydrogels, which are extremely popular and widely utilized today. Specifically, silicone hydrogel contact lenses that are available today combine the benefit of silicone, which has extremely high oxygen permeability, with the proven comfort and clinical performance of hydrogels. Essentially, these silicone hydrogel based contact lenses have higher oxygen permeabilities and are generally more comfortable to wear than the contact lenses made of the earlier hard materials. However, these new contact lenses are not totally without limitations.
Contact lenses may be worn by many users for eight (8) hours to several days in a row without any adverse reactions such as redness, soreness, mucin buildup and symptoms of contact lens related dry eye. However, some users begin to develop these symptoms after only a few hours of use. Many of those contact lens wearers use rewetting solutions to alleviate the discomfort associated with these adverse reactions with some success. However, the use of these solutions requires that users carry extra solutions and this may prove to be inconvenient. For these users a more comfortable contact lens that does not require the use of rewetting solutions would be useful.
Potential problems associated with contact lens wear may affect the eyelid, the conjunctiva, the various layers of the cornea and the tear film that covers the outer surface of the eye.
When a contact lens is positioned on the eye, layers of tear film form both between the back curve or posterior surface of the contact lens and the cornea as well as over the anterior surface of the contact lens. It is beneficial to refresh tears or the tear film in both regions in order to remove contaminants that build up in the tear film, and it is particularly beneficial to refresh the tear film behind the contact lens or more precisely the tear film between the posterior surface of the contact lens and the cornea. Accordingly, there exists a need for an improved contact lens that facilitates tear exchange posterior to the contact lens.